The overall purpose of this K22 Scholar Development and Faculty Transition Career Award is to provide additional (1 year) postdoctoral mentorship and support to the principle investigator in the area of advancing photopolymerizable hydrogels for cartilage tissue engineering in addition to support (4 years) as an independent faculty member to continue research in this field. The proposed research originated to complement the principle investigator's background in the development of novel photocrosslinkable biomaterials for bone tissue engineering with a long-term objective of developing complex materials at the interface of bone and cartilage for craniofacial applications. It is the general goal of the principle investigator to develop an internationally recognized research laboratory that uses the synthesis and modification of novel materials as a platform for the development of clinically relevant therapeutics. The proposed research and career development program outlined in this proposal were developed by the principle investigator and Mentors from both the Massachusetts General Hospital and Massachusetts Institute of Technology in an effort to achieve this goal. Photopolymerizable hydrogels have many properties that are beneficial for cartilage tissue engineering including: the ability to form in vivo to fill complex defects with potential adhesive and integrative properties, both spatial and temporal control over the polymerization process, and biological signals are readily incorporated into the networks to control both cellular differentiation and tissue formation. These properties would be extremely beneficial for the regeneration of cartilage in craniofacial reconstruction. With these benefits in mind, the primary aims of the proposed research are to: . synthesize and characterize photopolymerizable copolymer hydrogel networks that resorb via an enzymatic degradation process, . investigate the quantity, distribution, and type of tissue formed by chondrocytes encapsulated in hydrogel networks as a function of hydrogel composition, . incorporate signals into hydrogel networks to control the chondrogenic differentiation of photoencapsulated mesenchymal stem cells, and . analyze critical issues of the photopolymerized constructs necessary for clinical application of these techniques.